This invention relates to an actuator for high voltage air break electrical switches.
Prior art air break switches are relatively large switches which require significant force to operate. Such switches are usually mounted on top of power poles and are designed to immediately break the power supply along an overhead high voltage distribution line or number of lines. Present air break switches are activated by manually operated handles. These handles are located at the base of a power pole to which access is only available to authorized maintenance crews. Prior art air break switch actuators usually comprise a lever mechanism biased to open or close a switch and to hold the switch in the open or closed position. The biasing action is normally due to a powerful spring under compression between two points corresponding to the switch""s open or closed positions. The spring applies force in either direction away from a position between the open and close positions to the lever operating the switch which is also held in the open or closed position by the force of the spring. This introduces certain problems mainly that when the actuator is driven in a reverse direction, the spring pressure is relieved from the air break switch for the time that the spring travels to a changeover point. At the changeover point the spring commences to open or close the switch by applying force in the relevant direction. The problem is when spring force which is holding the switch closed is removed the switch contacts for this brief period are only held together by gravity with the potential for arcing should they commence to separate due to some external force or pressure. Importantly, the force required to open a switch is greater than the force required to close a switch. As a result, actuators therefore are limited to springs which are large enough to provide enough force to open the switch. It is the inventor""s observation that prior art actuators do not have the ability to vary the spring force as required to open or close the switch so that more compact and springs which apply less force to the switch mechanism can be used. In addition, as prior art actuators have an exposed sliding slot mechanism, they are prone to be vandalised and can be affected by adverse weather conditions such as the mechanism icing up, being corroded by salt in a marine environment and/or jamming due to the nesting activities of birds and bird droppings.
Utilising existing ball screw linear drives and associated electronics, it is now possible to operate air break switch actuators remotely by means of radio control. This negates the necessity for maintenance crew have to travel to a fault site in order to operate the air break switch to disconnect power along the relevant faulty line or lines. The switch can be actuated well in advance to limit or prevent further damage to the grid and to isolate faulty sections of line. The introduction of remote control mechanisms, however requires efficient and smooth operation of the actuator apparatus. Prior art switch actuators which may be affected by weather, vandals or jammed by other factors present a significant reliability problem in terms of remote or radio controlled operation.
It is therefore an object of the present invention to alleviate to some degree some of the problems associated with prior art air break switch actuators or to at least provide the public with a useful choice.
In a first aspect the present invention consist in an air break switch actuator comprising or including:
a structure providing means to locate in position,
a switch actuating means adapted to move between a first and a second position corresponding to an open or a closed position, or vice versa, of a switch,
operating means, operable manually and/or by a drive unit,
a connection means connecting the operating means with the switch actuation means to positively displace the switch actuation means at least during part of the movement of the operating means
biasing means applying, directly or indirectly at least during part of the movement of the switch between the first and second positions, a biasing force to urge the actuating means to the first or the second position.
Preferably the biasing means acts directly or indirectly at least during part of the movement of the switch between the first and second positions, to bias the switch actuating means away from a snap through region of movement thereof, in a direction towards the first or second position.
Preferably said biasing means acts on the connection means to bias the connection means via a linkage means, there being provided as part of said linkage means a trigger means to move the direction of the biasing force applied by the biasing means to the connection member dependent on the position of said connection.
Preferably said trigger means is engaged to the linkage mechanism and becomes operative, to move the direction of the biasing force when said connection means is at the snap through region, by being displaced by the movement of said connection means.
Preferably said linkage means is configured such that said trigger is actuated by the movement of said connection means to advance the snap though point to occur earlier in said snap though region.
Preferably said switch actuating means comprises a switch lever rotatably movable about lever axis between two positions corresponding to the open and closed positions of said switch.
Preferably said operating means comprises an operating lever rotatably movable about said lever axis between two positions corresponding to the open and closed positions of said switch.
Preferably said connection means is a plate which is rotatable about said lever axis and includes a connection member for engagement and to provide positive displacement by the operating means, to the switch actuating means at least during part of the movement of the operating means.
Preferably said operating means includes an operating plate directly connected to and for rotation by said operating lever, said operating plate having at least one slot, concentric with said lever axis, with which said connection member of said connection means is engaged at least during rotation of said operating means towards said snap through point, said connection means is rotatably displaced by the movement of said operating plate up to the point at which snap through occurs.
Preferably said switch actuation means includes a switch plate directly connected to said switch lever to operate the rotation of said switch lever respondent to the displacement thereof by the connection member.
Preferably said switch plate includes as least one slot, concentric with said lever axis, with which the said connection member of said connection means is engaged to displace said switch plate at least through and beyond said snap though point.
Preferably said at least one slot of said switch plate is of identical shape to the at least one slot of said operating plate.
Preferably said at least one slot of said operating plate, when said connection plate is at its extremes of rotation, is in alignment with the at least one slot of said switch plate.
Preferably said connection plate is intermediate of the operating plate switch plate, said connection member being a transverse pin extending into the slots of the connection plate.
Preferably said operating plate has two slots and said switch plate has two slots, said connection plate providing two connection members, one for each of the pairs of slots.
Preferably said linkage means includes a connection rod acting directly on and at a circumferential point of the connection plate, said connection rod connected to a crank pivoted about a fulcrum provided by said trigger arm, wherein said biasing means is provided to act on said crank to bias said connection rod toward said connection plate.
Preferably said trigger arm is pivotably located to said structure providing means to displace said fulcrum with a component of movement in a direction tangential to the arc of movement of the connection point of the connection rod to the connection plate.
Preferably a locking means is movably mounted from said structure providing means to selectively lock the switch plate from rotating when said switch is in either the first or the second position.
Preferably said locking means is at least one pawl member pivotable with respect o the structure providing means to move between a retracted condition and a locking position, wherein in a locking position it is able, when aligned with, to engage with a complementary shaped notch of catch of said switch plate.
Preferably said locking means is movable from said engaged condition to said retracted condition, respondent to the rotational position of said connection plate, by a cam follower which follows the contour of an appropriately shaped cammed surface of said connection plate.
Preferably said locking means is movable from said retracted condition to said engaged condition, respondent to the rotational position of said connection plate, by a cam follower which is biased towards and to follow the contour of an appropriately shaped cammed surface of said connection plate.
In a second aspect the present invention consists in a switch actuator to move a switch between a first and second position corresponding to an open and closed position of the switch, said actuator comprising or including:
a first rotatable member in mechanical connection with and to move said switch between said open and closed position by the rotation of said rotatable member about an axis,
a second rotatable member in mechanical connection with an actuator, and rotatable about said axis
a connection member rotatable about said pivot axis, said connection member biased by a biasing means for rotation about said pivot axis in a toggle manner between a first angular position and a second angular position, said connection member providing a mechanical connection means to locate
(a) against a fixed point of, and be displaced by, said second rotatable means at least during the rotation of the connection member by the second rotation means towards the point of toggle of the connection means, and
(b) against a fixed point of and to thereby displace, the first rotatable member at least during rotation of said connection member passed said point of toggle.
Preferably said fixed points of said first and second rotatable members are the distal ends of at least one slot provided in each of said first and second rotatable members, said mechanical connection means extending into each of said slots.
Preferably said biasing means acts on the connection member to bias the connection member via a linkage means, there being provided as part of said linkage means a trigger means to move the direction of the biasing force applied by the biasing means to the connection member dependent on the angular position of said connection member.
Preferably said trigger means is engaged to the linkage member and becomes operative to move the direction of the biasing force, when said connection member approaches a point of rotation nearing the toggle point, by being triggered by the movement of said connection member.
Preferably said linkage means is configured such that said trigger is actuated by the movement of said connection member to advance the toggle point to occur earlier in the rotation of said connection member.
In a further aspect the present invention consists in the use of an actuator as hereinbefore described for the control of an air brake switch between an open and closed position of the air brake switch.
In still a further aspect the present invention consist in an air break switch actuator to including in combination:
a housing adapted to enclose in position,
a switch actuating means adapted to move between a first and a second position corresponding to an open or a closed position, or vice versa, of a switch,
operating means to operate said actuating means, the operating means manually operable and/or driven by a linear drive unit,
releasable locking means adapted to lock the actuating means in either the first or the second position,
biasing means adapted to apply a biasing force to urge the actuating means to either the first or the second position,
linkage means coupling the operating means with the locking means and the biasing means, the linkage means adapted to change the direction and strength of the biasing force between said first and second portions,
wherein in operation, the operating means disengages the locking means and causes the actuating means to move from the first to the second position and at the same time overcoming the biasing force of the biasing means; the linkage means changing the direction and strength of the biasing force to urge the actuating means from the first to the second position, the locking means then re-engaging and locking the actuating means in the second position, the operation repeatable between first and second positions as required.
Preferably the actuating means comprises a switch lever movable between two positions and joined to a slotted switch plate, the switch lever connected by connecting rods or other means to open or close the air break switch.
Preferably the operating means includes a manually or motor driven crank, the crank connected to a motor plate having slots which at least in one position is in corresponding alignment with the slots of the switch plate, the motor plate engaging the switch plate by means of a spring plate intermediate the motor plate and the switch plate wherein the spring plate has transverse pins engaging the slots of the motor and switch plates, the motor plate, spring plate and switch plate in coaxial alignment and rotatable about an axial shaft. Preferably the linear drive unit is a linear electrical actuator with a mechanical clutch at both ends of travel to prevent damage to the actuator in the event of jamming or failure of any of the actuator""s components. Such an electrical linear actuator enables the spring actuator to be remotely operated.
Preferably the locking means comprises one or more pawl members pivotal about an axial member at one end and having one or more sprags engageable with notches in the switch plate. The sprags of the pawl members are disengageable from the notches by means of a cam action of the springplate whereby one or more cam lobes on the spring plate in contact with one or more cam following portions of the pawl members pivots the pawl members away from the switch plate.
The biasing means is preferably a spring under compression operating through a lever connected by an extension arm to a lug on the spring plate.
The crank operating through the linkage members compresses the spring and cause the spring plate to rotate from the first to the second position until the direction of the spring""s force is changed by the linkage members so that the compression of the spring is released to drive the spring plate and the switch plate to the second position. On reaching the second position the pawl members are re-engaged with the switch plate thereby locking the switch plate in the second position.
To return the switch plate to the first position, the order of the operation is reversed by the crank to change the rotation of the spring plate in the direction of the first position wherein the pawl members are disengaged from the switch plate by the cam action of the spring plate. The spring is recompressed until the direction of the spring force is changed by the linkages member wherein the spring is again released from its compressed state to return the spring plate and the switch plate to the first position.
Preferably the biasing means includes adjustment means for adjusting the tension of the spring.
Preferably the engagement of the sprags of the pawl members with the notches of the switch plate is under spring tension and is adjustable.